TY - JOUR

T1 - Accounting for Winter Warming Events in the Ecosystem Model LPJ-GUESS

T2 - Evaluation and Outlook

AU - Pascual, D.

AU - Johansson, M.

AU - Pongracz, A.

AU - Tang, J.

N1 - Publisher Copyright: © 2024. The Authors.

PY - 2024

Y1 - 2024

N2 - Winter warming events (WWEs) are short-lasting events of unusually warm weather, occasionally combined with rainfall, which can cause severe ecosystem impacts by altering ground temperatures and water fluxes. Despite their importance, how large-scale ecosystem models perform in depicting the impacts of WWEs remain largely unknown. The frequency and intensity of WWEs will likely increase further in the future, making it necessary to understand their potential impacts on high-latitude ecosystems. In this study, we evaluated the ability of the dynamic ecosystem model Lund-Potsdam-Jena General Ecosystem Simulator (LPJ-GUESS) to represent the responses of subarctic ecosystems to future WWEs, and identified model gaps hindering more accurate estimates of these responses. In response to WWEs, the model simulated substantial ground cooling (up to 2°C in winter) due to reduced snow depth (insulation), with rain on snow (ROS) exerting a marginal influence on the ground temperature responses: these modeled responses are in apparent contradiction with the strong ground warming effect of ROS reported in most observational studies. The simulated ground cooling led to changes in biogeochemical fluxes that were substantial and often comparable in magnitude (but often opposite in direction) to those from altered winter climatologies. The mismatch between the modeled and the observed ground temperature responses to WWEs highlights LPJ-GUESS's current limitations in realistically simulating some of the effects of WWEs. These limitations likely stem from the (a) absence of a surface energy balance, (b) lack of snow-vegetation interactions, (c) daily time-step, and (d) simplistic water retention scheme in LPJ-GUESS.

AB - Winter warming events (WWEs) are short-lasting events of unusually warm weather, occasionally combined with rainfall, which can cause severe ecosystem impacts by altering ground temperatures and water fluxes. Despite their importance, how large-scale ecosystem models perform in depicting the impacts of WWEs remain largely unknown. The frequency and intensity of WWEs will likely increase further in the future, making it necessary to understand their potential impacts on high-latitude ecosystems. In this study, we evaluated the ability of the dynamic ecosystem model Lund-Potsdam-Jena General Ecosystem Simulator (LPJ-GUESS) to represent the responses of subarctic ecosystems to future WWEs, and identified model gaps hindering more accurate estimates of these responses. In response to WWEs, the model simulated substantial ground cooling (up to 2°C in winter) due to reduced snow depth (insulation), with rain on snow (ROS) exerting a marginal influence on the ground temperature responses: these modeled responses are in apparent contradiction with the strong ground warming effect of ROS reported in most observational studies. The simulated ground cooling led to changes in biogeochemical fluxes that were substantial and often comparable in magnitude (but often opposite in direction) to those from altered winter climatologies. The mismatch between the modeled and the observed ground temperature responses to WWEs highlights LPJ-GUESS's current limitations in realistically simulating some of the effects of WWEs. These limitations likely stem from the (a) absence of a surface energy balance, (b) lack of snow-vegetation interactions, (c) daily time-step, and (d) simplistic water retention scheme in LPJ-GUESS.

KW - arctic ecosystems

KW - carbon cycle

KW - climate extremes

KW - modeling

KW - rain on snow

KW - winter warming events

U2 - 10.1029/2023JG007464

DO - 10.1029/2023JG007464

M3 - Journal article

AN - SCOPUS:85187445380

VL - 129

JO - Journal of Geophysical Research: Solid Earth

JF - Journal of Geophysical Research: Solid Earth

SN - 0148-0227

IS - 3

M1 - e2023JG007464

ER -